The present invention relates to a head gimbal assembly (HGA) with a precise positioning actuator for a head element such as a thin-film magnetic head element or an optical head element.
In a magnetic disk drive apparatus, thin-film magnetic head elements for writing magnetic information into and/or reading magnetic information from magnetic disks are in general formed on magnetic head sliders flying in operation above the rotating magnetic disks. The sliders are supported at top end sections of suspensions of HGAs, respectively.
Recently, recording and reproducing density along the radial direction or along the track width direction in the magnetic disk (track density) has rapidly increased to satisfy the requirement for ever increasing data storage capacities and densities in today""s magnetic disk drive apparatus. For advancing the track density, the position control of the magnetic head element with respect to the track in the magnetic disk by only a voice coil motor (VCM) has never presented enough accuracy.
In order to solve this problem, an additional actuator mechanism is mounted at a position nearer to the magnetic head slider than the VCM so as to perform fine precise positioning that cannot be realized by the VCM only. The techniques for realizing precise positioning of the magnetic head are described in for example U.S. Pat. No. 5,745,319 and Japanese patent publication No. 08180623 A.
The HGA with such a precise positioning actuator is required to have a sufficient high resonance frequency of the suspension to provide a high speed servo-operation.
In general, a load applied to the magnetic head slider is adjusted by means of a bending section additionally formed as a part of a load beam of a suspension near a base plate. Namely, the load beam at a position near the base plate is slightly bent to form the bending section so that a top end section of the load beam presses the magnetic head slider mounted toward a magnetic disk. The load applied to the magnetic head slider can be adjusted by controlling a bend angle of this bending section.
However, forming of such a bending section onto the load beam greatly lowers a resonance frequency of the whole suspension due to a complex shape of the bent load beam. Thus, the lowered resonance frequency may be laid within a frequency band used for the servo mechanism making a high speed operation of the servo difficult.
Also, if such a bending section is formed onto the load beam, the suspension will be seriously susceptible to wind resistance. Namely, side winds produced due to a high-speed rotation of the magnetic disk will be directly applied to and thus exert a large influence upon the bending section causing random vibrations of the suspension to occur. Particularly, the influence of the wind resistance becomes large in case of a recent high end HDD in which the magnetic disk rotates at a high speed of 10,000 to 15,000 rpm or more.
Furthermore, since the bending section has a low stiffness, a top end section of the suspension will receive a large impact if a shock toward its up-and-down directions (Z-directions) is applied to the suspension causing making a shock resistance of the whole suspension extremely poor.
In addition, according to the conventional HGA with a bending section for adjusting a load applied to the magnetic head slider by controlling its bent bend angle, not only the fabrication process is complicated but also a precise adjustment of the load cannot be expected. Particularly, because the load value to be adjusted decreases as the magnetic head slider becomes light in weight, any variation in the adjusted load cannot be negligible and therefore load tolerance increases.
It is therefore an object of the present invention to provide an HGA with a precise positioning actuator for a head element, whereby a resonance frequency of the HGA can be increased.
Another object of the present invention is to provide an HGA with a precise positioning actuator for a head element, whereby wind-resistance performance of the HGA can be increased.
Further object of the present invention is to provide an HGA with a precise positioning actuator for a head element, whereby a resistance against a shock of in Z-directions can be increased.
Still further object of the present invention is to provide an HGA with a precise positioning actuator for a head element, whereby a manufacturing process of the HGA can be simplified and a load tolerance can be kept small.
According to the present invention, an HGA includes a head slider provided with at least one head element, a load beam, a flexure fixed to the load beam for determining a flying attitude of the head slider, a precise positioning actuator fixed to the head slider and supported by the flexure, for precisely positioning the at least one head element, and a load adjustment mechanism formed with the actuator, for adjusting a load imposed on the head slider.
The actuator is provided with a load adjustment mechanism for adjusting a load imposed on the head slider. Therefore, it is unnecessary that the load beam of the HGA has a bending section for imposing a load, and thus the load beam can be formed by a member with a sufficient stiffness resulting in increasing a resonance frequency of the suspension. Accordingly, a frequency band for a servo can be broadened and thus a high speed seek operation of the servo can be expected. The increased stiffness of the suspension provides improvement in a shock resistance of the HGA against a Z-direction impact.
Also, since the load beam which has a large side sectional area and receives side winds with no bending section for imposing a load, influence of wind resistance can be suppressed to a minimum. Furthermore, since the imposed load is adjusted by controlling the load adjustment mechanism instead of controlling a bending angle of a bending section, not only a manufacturing process of the HGA can be simplified and a manufacturing cost of the HGA can be reduced, but also the imposed load can be adjusted with a high accuracy and a small tolerance.
It is preferred that the load adjustment mechanism is formed directly underneath a load point onto the head slider.
It is also preferred that a projection or a dimple formed on the load beam functions as the load point.
It is preferred that the load adjusting means includes a spring plate section for controlling the load imposed on the head slider, and that one end of the load adjusting means is a free end.
It is further preferred that the actuator is formed from a multilayer plate member. In this case, it is more preferred that the multilayer plate member includes a first thin metal plate layer, a resin layer laminated on the first thin metal plate layer and a second thin metal plate layer laminated on the resin layer, and that the spring plate section is formed by a part of the first or second thin metal plate layer.
It is also preferred that the actuator is formed from a single-layer metal plate member. In this case, it is more preferred that the load adjustment mechanism includes the single-layer metal plate member and a spacer laminated on the single-layer metal plate member, and that the spring plate section is formed by a part of the single-layer metal plate member.
It is further preferred that the actuator is unitarily formed with the flexure, or individually formed from the flexure.
Preferably, the load beam is a straight shaped load beam to have a high stiffness. In this case, the load beam may consist of a single plate member. The load beam may have no load adjustment mechanism for adjusting a load imposed on the head slider.
It is also preferred that the HGA further includes a back-bending section capable of bending a part of the HGA at the time of mounting of the HGA to an HDD.
It is preferred that the actuator includes a pair of movable arms each formed by a multilayer plate member or a single-layer metal plate member that is substantially in parallel with a side surface of the head slider, top end sections of the pair of movable arms being capable of displacing in response to a drive signal applied to the actuator along directions crossing a plane of the multilayer plate member or the single-layer metal plate member, and a coupling section connected between the top end sections of the pair of movable arms and formed by a multilayer plate member or a single-layer metal plate member that is substantially in parallel with a one surface of the head slider, the one surface being opposite to an air bearing surface (ABS) of the head slider, and that the one surface of the head slider is fixed to the coupling section.
Since the actuator is provided with the coupling section connected between the top end sections of the pair of movable arms and the head slider is to be fixed to this coupling section, fixing of the slider can be achieved with sufficient strength and a shock resistance against up-and-down movements can be greatly improved. Also, head sliders with different widths can be easily mounted to the actuator.
Further, the movable arms and the coupling section are mainly made from the multilayer plate member or the single-layer metal plate member, the weight of the whole actuator can be reduced and thus a mechanical resonance frequency of the actuator can be increased. Also, as a basic member of the arms is formed by the multilayer plate member or the single-layer metal plate member that is strong and light-weighted, a shock resistance of the movable arms that are particularly weaken for the shock can be greatly improved. Due to the usage of the multilayer plate member or the single-layer metal plate member provided with a high mechanical strength, treatment of the actuator during assembling of the HGA becomes very easy. By using the multilayer plate member or the single-layer metal plate member to form the main portion of the actuator, the flexibility on a design of the actuator will improve with the shape and/or size. Thus, it is enabled to design the actuator with a sufficient stroke. Furthermore, because the multilayer plate member or the single-layer metal plate member can be precisely machined, accuracy in size of the actuator itself can be greatly improved.
Also, since the head slider is mounted in a space between the movable arms, the thickness of the HGA (Z-height) around the head slider does not increase even if the actuator is attached. Thus, no modifications in size of the disk drive apparatus due to the mounting of the actuator is necessary. In addition, since the head slider is caught in between the movable arms, the top end sections of the movable arms, which actually transfer the displacement to the slider, can be extended to always position at the top end of the slider. Thus, it is possible to provide a constant travel to the slider even if the size of the head slider changes, and therefore an enough stroke of the head at the precise positioning operation can be always obtained.
Because of a partial fixing of the head slider to the coupling section of the actuator, shape change in the ABS of the head slider (generation of crown or camber) can be prevented from occurring even if the adhesive deforms due to change in atmosphere temperature.
It is also preferred that the actuator further includes a base section formed by a multilayer plate member or a single-layer metal plate member that is in parallel with the coupling section, wherein the base section is fixed to or united with the flexure, and that the pair of movable arms extend forward from the base section. As not only the movable arms and the coupling section but also the base section are made from the multilayer plate member or the single-layer metal plate member, the weight can be more reduced and a shock resistance can be more improved. Also, accuracy in size of the actuator itself can be greatly improved.
It is further preferred that the pair of movable arms, the coupling section and the base section of the actuator have a U-shaped section structure formed by bending a multilayer plate member or a single-layer metal plate member. Since the main portion of the actuator is configured by bending the multilayer plate member or the single-layer metal plate member, its fabrication becomes easy and a mechanically strong actuator can be provided.
It is preferred that each of the pair of movable arms of the actuator includes an arm member formed by a multilayer plate member or a single-layer metal plate member, and a piezoelectric element formed or adhered on a side surface of the arm member. In this case, the piezoelectric element may have a multilayer structure of piezoelectric material layers and of electrode layers, or a single-layer structure of a piezoelectric material layer and of an electrode layer. If the piezoelectric element is formed in the multi-layered structure, sufficient displacement will be obtained at low drive voltage and a horizontal shock resistance will be increased.
It is also preferred that the coupling section of the actuator is fixed to the head slider by an adhesive.
It is preferred that the at least one head element is at least one thin-film magnetic head element.
Further objects and advantages of the present invention will be apparent from the following description of the preferred embodiments of the invention as illustrated in the accompanying drawings.